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Abstract

To address the requirements of multi-level semiconductors, we propose a new technique for overcoming the height limitation of direct laser lithography. In the proposed system, an original source beam is fed into an interference generator that divides the input beam by 50: 50 into two output beams. After going through an imaging lens, these two beams make two focusing spots, which are slightly separated in the axial direction. In the overlapped region, these two spots generate a small interferogram that shortens the depth of focus. By using this phenomenon, we are able to overcome the height limitation of direct laser lithography. The governing equations are also derived in this manuscript by using the Gaussian beam model.

Figures (9)

(a) Fabrication of a pattern in multiple layers, and (b) after etching process. Undesired defects commonly occurred when the depth of focus (DOF) of the lithographic system was larger than the thickness of the layer.

Fabricated result on the multi-level layer. (a) Test flan, (b) after the photoresist film etching, and (c) then after the chromium etching. The 3D profiles shown in (b) and (c) were obtained by the white-light scanning interferometer.